This application is based on and claims the priority under 35 U.S.C. xc2xa7119 of German Patent Application 100 61 636.4, filed on Dec. 11, 2000, the entire disclosure of which is incorporated herein by reference.
The invention relates to a rotor blade with a flap and a flap drive, wherein the lift-generating blade accommodates the flap drive with the flap, but the flap remains arranged outside the blade.
The rotor system of a helicopter is the cause of noise and vibrations in the cabin. At the same time the rotor system generates a high external noise level, particularly during the landing flight. These noise emissions and vibrations result in an extreme reduction in comfort for helicopter passengers and prove to be unfavorable to the environment. During the course of further helicopter construction developments, the aim is to reduce these noise emissions and vibrations.
In the case of the helicopters presently offered on the market with conventional rotor systems, the rotor blades are collectively and cyclically controlled via a swash plate and a mechanical connecting rod linkage. The idea of extending this primary rotor blade control by using a flap fitted in the blade tip area of the individual rotor blade is now generally accepted for reducing noise emissions and vibrations. This flap is intended to enable individual blade control. By using a controllable flap in the lift-generating blade area, preferably close to the blade tip and at the profile trailing edge of the blade, it is possible for the rotor blade to continuously adjust to the varying air flow conditions during a rotor blade rotation, thus allowing a reduction in noise emissions and vibrations via the rotor system.
Published European Patent Application EP 1,035,015 A2 describes a flap drive with a flap, which is installed in a rotor blade. The flap drive consists of an actuator, a movable hinged frame coupled with the actuator and from there, via a power transmission means, with a pivotably mounted flap. The actuator is fastened to the inner structure of the rotor blade and the blade is mounted in the rotor blade structure in such a way that it can pivot. During the manufacture of the rotor blade, the flap drive with the flap must be installed in the rotor blade at the same time.
In order to allow a visual inspection of the flap drive and to allow maintenance work to be performed, an opening will be left in the rotor blade shell, which can be closed with a cover. The opening in the rotor blade has a detrimental influence on the blade supporting structure. Structural properties such as bending rigidity and strength are detrimentally influenced by the penetration through the shell. The closing cover of the opening must be formed as a component of the supporting structure. That usually results in a detrimental change to the aerodynamic blade properties in the existing blade geometry. If, finally, the flap drive is closed within the blade, then it will be necessary to exchange the entire rotor blade due to any arising problems in the flap drive.
It is an object of the invention to structure the installation of a flap with a flap drive in a rotor blade in such a way, that the structure of the rotor blade is hardly influenced and still allows a rapid inspection of the serviceability of the flap, as well as its adjustment and maintenance. The invention further aims to overcome or avoid the disadvantages of the prior art, and to achieve additional advantages, as apparent from the present specification.
The above objects have been achieved in a rotor blade arrangement according to the invention. The lift-generating blade has a blade chamber formed in its structure, with an opening pointing in the direction of the trailing edge. When the rotor blade is at rest, and being initially manufactured, or later serviced or retro-fitted for example, at least one housing can be inserted through this opening into the blade chamber and then releasably fixed therein. The housing accommodates at least one flap drive and the flap. Alternatively, the blade chamber can be formed with an opening pointing in the direction of the leading edge nose. The housing there supports at least one leading edge flap or nose flap with a leading edge flap drive. The housing with its associated flap and flap drive form an exchangeable flap module that is removably and exchangeably secured in the blade chamber of the blade.
In the area of the outer skin or shell of the rotor blade, a flexible elastic bending cover is formed as a boundary to the blade chamber, the bending hinge axis of which is essentially guided lengthwise and parallel to the longitudinal blade axis. The bending cover can pivot or deflect from a resting position into an end position and back again. In this way the opening of the chamber can be enlarged in order to insert or remove the housing.
When inserting and removing the housing in the blade chamber, the blade chamber walls serve as a guide for the housing. Furthermore, the housing also supports a pre-tensioning means for the pre-tensioning of a flap drive piezoactuator.
The housing can be positioned in the blade chamber and fixed by a fastening means. Furthermore, the housing has a connecting means arranged therein for connecting relevant components (e.g. the actuator) in the housing with the power and information wires leading through the rotor blade.
The housing is positioned in the blade chamber of the rotor blade in such a way that the center of gravity of the profile cross-section of such a rotor blade is hardly altered in comparison with an original profile cross-section without the blade chamber. The center of gravity of the housing is arranged close to the leading edge spar in the housing interior.
The housing accommodated in the blade chamber supports seal elements or means, which allow the blade chamber opening to be sealed, thus avoiding the penetration of dust particles and humidity.
It is also possible to arrange plural individual housings next to each other on one plane in the direction of the longitudinal blade axis, in a blade chamber having appropriately large dimensions, thus allowing an increase in the effective flap length in the longitudinal direction of the blade.
The structure of the rotor blade is hardly influenced by the invention. The use of the flap module allows its rapid onsite inspection and also allows a rapid maintenance and adjustment of the flap drive and the flap. To accomplish this, the rotor blade does not even need to be removed from the rotor hub. If necessary, the flap module may simply be removed from the blade chamber and replaced with a different flap module, e.g. a new module or a module that has been repaired, upgraded or maintenance-serviced.